Claw pole rotating electric machine

ABSTRACT

A claw pole type rotating electric machine comprising first and second claw cores which are disposed on a ring shaped ring yoke portion and a plurality of claw magnetic poles which extend in the axial direction are provided, and stator cores are formed by meshing of the claw magnetic poles with each other, and the stator is formed by holding the ring coils on the outer circumference side of the claw magnetic poles, wherein the first and second claw cores are formed by powder cores, the radial direction thickness of the claw magnetic pole is 2 mm or more, a flat surface is formed perpendicular to the axial direction at the end extending in the axial direction of the claw magnetic pole, a ejection taper in the circumference direction of the claw magnetic pole is formed in the range of 10 degrees or less, and the ratio of the axial direction length of the claw magnetic pole and the axial direction thickness of the ring yoke portion is no more than 5:1.

CLAIM OF PRIORITY

The present application claims priority from Japanese application Ser.No. 2005-286634, filed on Sep. 30, 2005 and Japanese application Ser.No. 2006-239694, filed on Sep. 5, 2006, the content of which are herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a claw pole type rotating electric machinewhich has a claw type magnetic pole.

2. Description of the Prior Art

In the typical rotating electric machine, much attention has been givento claw pole type rotating electric machines equipped with a stator corewhich has a claw type magnetic pole, in order to increase the spacefactor of the winding and improve utilization of magnetic flux.

In addition, in the claw pole type rotating electric machine of theprior art, in order to form the plurality of claw magnetic poles of thestator core, as is the case in Japanese Patent Laid-Open No. 2004-68041for example, magnetic poles may be formed by compacting of the softmagnetic powder.

SUMMARY OF THE INVENTION

According to the technology of the prior art in which the claw magneticpole is formed by compacting of soft magnetic powder, there is theadvantage that the claw magnetic pole can be formed in a 3-D shape, butgenerally there is a problem in that, the claw magnetic poles formed bycompacting of these magnetic powders have inferior magnetic propertieswhen compared to the claw magnetic pole motor formed using a cold-rolledsteel plate.

The object of this invention is to provide a claw pole type rotatingelectric machine in which even when the claw magnetic pole is formed bycompacting of magnetic powder, magnetic properties which are greaterthan that of the claw magnetic pole of the cold-rolled steel plate canbe obtained.

[Means for Solving the Problems]

In order to achieve this object, there is a claw pole type rotatingelectric machine comprising a ring yoke portion and first and secondclaw cores which are formed of a plurality of claw magnetic poles whichare disposed at equal intervals on the circumference of the innerdiameter side of the ring yoke portion and extend in the axialdirection, and a stator core formed by meshing of the claw magneticpoles of the first and second claw cores with each other, and a statorformed by holding the ring coil on the outer circumference side of theclaw magnetic poles in which the stator cores have been meshed, and arotor positioned via a space in the circumferential direction at theinner diameter side of the stator wherein, the first and second clawcores are formed by compacting of magnetic powder and the radialdirection thickness of the claw magnetic pole is 2 mm or more and a flatsurface is formed perpendicular to the axial direction at the endextending in the axial direction of the claw magnetic pole, and at theclaw magnetic pole, a ejection taper in the range of 10 degrees or lesswith respect to the axial direction is formed as a taper from the baseto the end extending in the axial direction, and the ratio of the axialdirection length of the claw magnetic pole and the axial directionthickness of the ring yoke portion is no more than 5:1.

In this manner, because the thickness of the claw magnetic pole is 2 mmor more, and the flat surface is formed perpendicular to the axialdirection at the axial direction free end of the claw magnetic pole, andthe axial direction width angle of the claw magnetic pole is formed as ataper from the base to the axial direction free end is no more than 10degrees, and the ratio of the axial direction length of the clawmagnetic pole and the axial direction thickness of the ring yoke portionis no more than 5:1, the magnetic powder can be subjected to compactingat high pressure, and consequently the density of the magnetic powdercan be increased, and so the magnetic properties can be improved so asto be greater than the claw magnetic pole formed using a cold-rolledsteel plate.

As described above, according to this invention, even for a clawmagnetic pole that is formed by compacting of magnetic powder, a clawpole type rotating electric machine that has magnetic properties greaterthan that of the claw magnetic pole made by the cold-rolled steel platecan be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the first claw core 11A and thesecond claw core 11B which comprise the stator core of the claw poletype rotating electric machine according to this invention.

FIG. 2 is a cross-sectional view of first claw core or the second clawcore of FIG. 1.

FIG. 3 is a back view of first claw core or the second claw core of FIG.1.

FIG. 4 is a front view of first claw core or the second claw core ofFIG. 1.

FIG. 5 is a vertical side surface view of claw pole type motor of thefirst embodiment of the claw pole type rotating electric machineaccording to this invention.

FIG. 6 is a chart showing a comparison of the magnetizing properties ofthe magnetic cores using various materials.

FIG. 7 is a mesh diagram for calculating the motor properties using athree-dimensional electromagnetic analysis.

FIG. 8 is a chart showing the relationship between the number of polesof the claw pole type motor and the output torque.

FIG. 9 is a chart showing the relationship between the average angle inthe circumferential direction of the claw magnetic pole of the claw poletype motor and the output torque.

FIG. 10 is an example of the structure of the claw pole type motor thatis formed cold-rolled steel plate (SPCC) of the prior art.

FIG. 11 is an example of comparison of the direct flow magneticproperties of SPCC and powder core.

FIG. 12 is an example of the results of comparison of the motor outputproperties of SPCC and powder core.

FIG. 13 is a comparative chart of the BH properties for each type ofmagnetic material.

FIG. 14 is a results chart in which the output torque is computed forthe claw pole type motor having a claw thickness of 2 mm using FEM.

FIG. 15 is the taper angle and the surface area of the claw magneticpole.

FIG. 16 is a schematic drawing showing the structure of the die forforming the stator core of the claw pole type motor of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the claw pole type rotating electric machine accordingto this invention is described based on the 24-pole claw pole type motorshown in FIG. 1-FIG. 5.

The claw pole type motor 1 is formed of a rotor 3 that is formed on therotating axle 2, a stator 6 that is provided coaxially via a minutespace G in the circumference direction with respect to the rotor 3, astator frame 8 which supports the stator 6, and bearings 9A and 9B thatsupport the rotating axle 2 so as to be rotatable at both end sides ofthe stator frame 8.

The rotor 3 comprises a rotor core 4 that is formed co-axially with therotating axle 2, and permanent magnetic pole 5 that are disposed inmultiples in the circumferential direction set at the outercircumference, and the stator 6 is formed of stator cores 7U, 7V and 7Wand the ring coil 10 that winds onto these stator cores 7U, 7V and 7W.In addition, the stator cores 7U, 7V and 7W are supported by the statorframe 8 and the rotating shaft 2 is supported onto both end portions ofthe stator frame 8 so as to be rotatable via the bearing 9A and 9B.

The stator cores 7U, 7V and 7W are formed from a first claw core 11A,and a second claw core 11B and the first claw core 11A, and the secondclaw core respectively and is formed of a claw magnetic pole 12 that hasa magnetic pole surface 12F which face the rotor 3 with a minute space Gand extends in the axial direction, a ring yoke portion 13 which extendsat right angles from the claw magnetic pole 12 to the outer diameterside, and an outer circumference side yoke 14 which extends in the samedirection as the claw magnetic pole 12 from the ring yoke portion 13.These magnetic poles 12 respectively form 12 poles at equal intervals inthe circumferential direction.

In addition, these first and second claw cores 11A and 11B are formed inthe same shape by compacting of magnetic powder by punch of a die, and amore complex magnetic pole structure can be obtained when compared tothat configured by layering silicon steel plates.

In this manner, first claw core 11A and the second claw core 11B thatare formed by compacting of magnetic powder are disposed such that endsextending in the axial direction 12T of the magnetic pole 12 are towardeach other, and by meshing the end extending in the axial direction 12Tis positioned between the matching side end extending in the axialdirection 12T, a plurality of magnetic pole surfaces 12F which areconcentric with the rotor 3 are formed along circumference surface ofthe rotor 3. At the same time, by the first claw core 11A and the secondclaw core 11B of each of the stator cores 7U, 7V and 7W and the axialend extending in the axial direction 12T meshing with each other, eachring coil 10U, 10V and 10W are held by the first claw core 11A and thesecond claw core 11B respectively, and the stator 6 is formed by these.

In this manner, the stator cores 7U, 7V and 7W which have ring coils10U, 10V and low built-in are connected in the axial direction, and byoffsetting the electrical angle by 120 degrees in the circumferentialdirection, a 3-phase claw pole type motor is configured.

In addition, by molding these 3 serial stator cores 7U, 7V and 7W froman insulating resin, a stator 6 can be obtained in which the first clawcore 11A and the second claw core 11B and the ring coil 10U, 10V and 10Ware integral.

As described above, by forming the first claw core 11A and the secondclaw core 11B by compacting of magnetic powder, a magnetic polestructure which is complex, or in other words, one obtaining improvedmotor efficiency can be obtained.

It is to be noted that, when the first claw core 11A and the second clawcore 11B are formed by compacting of magnetic powder, the magneticpowder is compacted using a die, but the direction of compacting is theaxial direction in which the claw magnetic pole 12 extends. At thistime, the punch for compacting of the first claw core 11A and the secondclaw core 11B must have punch cross-sectional area proportional to theaxial direction dimensions of the compact such that buckling of thepunch does not occur. In other words, the punch cross-sectional areamust be determined based on the axial direction dimension L1 of the clawmagnetic pole 12 at which the dimension in the axial direction ismaximum on the first claw core 11A and the second claw core 11B. Thus,the end extending in the axial direction 12T of the claw magnetic pole12 must have a flat surface which crosses the axial direction, and thesurface area of that flat surface must be made proportionately largesince the axial dimension L1 of the claw magnetic pole 12 is made large.Normally, in order to compact the magnetic powder and improve magneticproperties, about 10 ton/cm² of compacting pressure is needed, and asurface area corresponding to that is needed at the end extending in theaxial direction 12T of the claw magnetic pole 12. For this reason, theradial direction thickness H2 in the end extending in the axialdirection 12T of the claw magnetic pole 12 is at least 2 mm or more andthe surface area of the flat surface must be secured.

Furthermore, when the compact is removed from the die, a ejection taperθ is necessary in the axial direction, and must be formed on the clawmagnetic pole 12 to taper from the base to the end extending in theaxial direction 12T in the range of 8-10 degrees with respect to theaxial direction. In this type, at the time of compacting of the magneticpowder, a ejection taper 8 degrees or more is preferable when removingthe compact from the die, but when it is as large as possible, theejection operation is easier. However, when the ejection taper θ is madelarge, the surface area of the magnetic pole surface 12F of the magneticpole 12 is reduced and magnetic properties decrease, so the ejectiontaper θ is preferably 10 degrees or less which is small and for whichthere is little effect on magnetic properties.

Furthermore, the design is generally one where the gap magnetic poledensity between the rotor and the stator is 0.7-0.8 T. At this time, ifthe surface area of the claw is 5, the amount of the magnetic flux forone pole which flows into the claw is φ=BA and 3.5-4.0. In order for themagnetic flux to be absorbed by the yoke having thickness 1 (in the casewhere the ratio of axial direction length of the claw and the thicknessof the yoke is 5:1), the magnetic flux density at the time when enteredinto the yoke cross-sectional surface area 2 (thickness 1×2 times; it isdoubled here because the width of the yoke for one pair of poles isdouble the width of the claw for one pole) is B=φ/A and is 1.75-2.0 T,and cannot exceed 5:1 because this will be the saturation magnetic fluxdensity limit of the iron.

As described above, according to this embodiment, by-forming the firstclaw core 11A and the second claw core 11B as described above, themagnetic powder can be subjected to compacting at high compactingpressure and thus the density of powder core can be increased to 7.5g/cm³ or more, and as a result motor properties higher than magneticcores by cold-rolled steel plate (SPCC: a standard code of JapaneseIndustrial Standard) can be obtained.

This is also evident from the comparison of the magnetic properties ofthe magnetic cores from each material shown in FIG. 6. In FIG. 6, whenthe magnetic properties of the compacted powder magnetic core 1 formedby compacting of magnetic powder and a magnetic core from cold-rolledsteel plate (SPCC) and a magnetic core from a silicon steel plate(35A300, 50A1300) are looked at, the powder core 1 has small maximummagnetic flux density B (T) overall when compared with SPCC.

However, it was determined that because the first claw core 11A and thesecond claw core 11B of this embodiment have the aforementionedconfiguration conditions, high density of magnetic powder is achievedand powder core having density of 7.5 g/cm³ can be obtained and theyhave magnetic properties (magnetic flux density) closer to SPCC andSS400 compared to powder core having density of 7.3 g/cm³.

However, in the case where the powder core 1 which has a low density hasextremely low magnetic flux density and is used as a motor, the magneticproperties are reduced and the magnetic pole density is also low andthus in the case where a magnet whose residual magnetic flux density ishigh is used as the field magnet, output torque is reduced by saturationof the magnetic flux density and the like, and it can be expected thatthe magnetic properties will reduce.

The content described above will be described in more details usingproperties comparison of an actual motor. FIG. 10 shows the structure ofa claw pole type motor formed from cold-rolled steel plate (SPCC) of theprior art. This motor is formed by using a stator core that is formed bybending a steel plate such as SPCC and the like, and thus for smallmotors with a plate thickness φ of up to 100 mm for which bending ispossible, the limit is a thickness of about 1.6 mm. Meanwhile, thestator core of this claw pole type motor is formed of a powder core of adensity of 7.3 g/cm³ which can be compacted in this configuration. Theresults of comparison of the output properties at this time, for a motorformed in the same configuration are shown in FIG. 12. The claw poletype motor formed of SPCC of the prior art under the current comparisoncondition which are residual magnetic flux density of the field magnetof 1.2 T, 24 poles, rotation speed of 1000 r/min, magnetomotive force of220 ampere-turn, have a output torque that 10% higher compared to themotor that is formed of a powder core. The reason for this is, as shownin FIG. 11, when the direct current magnetizing properties of SPCC andpowder core are compared, the magnetic permeability of the powder coreis low, and the magnetic pole density when the same magnetic field isapplied is higher for SPCC.

However, there is no limit of the plate thickness of the powder core to1.6 mm or less due to the difference in the processing method. Becauseof this, it is possible to obtain a claw pole type motor with optimaldesign by increasing the degree of freedom of design by making the clawmagnetic pole thick and the like. The stator core which has beenoptimally designed under the conditions of the same field magnetaforementioned and the like has a claw thickness of 2 mm, and thecompacting pressure at the time of compacting can be made high and thusformation using a high density powder core becomes possible. The directcurrent magnetizing properties of the highly powder core whose densityis 7.5 g/cm³ are shown in FIG. 13. The magnetic permeability is improvedcompared to the direct current magnetizing properties of theaforementioned 7.3 g/cm³ powder core, but do not reach the magneticproperties of SPCC. The results of the calculations output torque arecomputed for the claw pole type motor having a claw thickness of 2 mmusing FEM. Manufacturing problems are disregarded and in thecalculations, the difference in output torque in the case where SPCC isused in the claw pole type motor and in the case where a powder corewhose density is 7.5 g/cm³ are compared. As shown in FIG. 14, the outputtorque in the case where the powder core is used is 20% higher. Thereason for this is, in the magnetic properties, SPCC has higher magneticpermeability, but in SPCC, because eddy current generated on the insideof the metal plate is generated in the direction crossing this magneticflux, this has the effect of contributing to reduction of the outputtorque. Due to this result, in a small motor of about φ100 mm, apermanent field magnet exceeding 1.2 T such as a rare earth sinteredmagnet having a high energy product is used as the field magnet, and theclaw pole type motor that is designed such that the claw thickness ofthe stator core is 2 mm or more can relax the effect of saturation ofmagnetic flux from the field magnet, and because it becomes possible toincrease the density of the powder core, it is clear that it is possibleto realize high motor properties. It is to be noted that the outputtorque of the motor is strongly influenced by the magnetic flux thatpasses through the claw magnetic pole, and thus a claw magnetic polewhose density is at least 7.5 g/cm³ or more is preferable.

Further, the results of studies about the ejection angle will bedescribed. In order to form the stator core of a high density powdercore, the aforementioned ejection taper is necessary, but when thistaper angle is increased, the surface area of the claw magnetic polebecomes small, and the output torque is reduced. FIG. 15 shows therelationship between the taper angle and the claw magnetic pole surfacearea. As shown in (a), when the configuration of the claw is defined andgiven that the claw magnetic pole surface area is 100% when the taperangle is 0, the changes in the surface area due to the taper angle isa·b−a²tanθ, and the relationship is that shown in (b). As shown before,when discussed in view of the compacting conditions of the powder core,the taper angle is preferably large, but in order to suppress motoroutput reduction is preferably small. As a result, the conditions forsatisfying motor properties that are greater than equal to theproperties for the motor formed of SPCC, require the taper angle to beup to 10° if output reduction of up to 20% is to be permitted.

Because it became possible to form the stator using a high density (highmagnetic flux density) compact core, it is possible to set a highmagnetomotive force using a magnet having a high residual magnetic fluxdensity as the field magnet. A rare earth magnet is used as thepermanent magnetic pole 5 of the rotor 3, and the magnetic flux densityis made 1.2-1.4 tesla, and the dimensional relationship of the firstclaw core 11A and the second claw core 11B corresponding to thismagnetic flux density was discovered by the following analysis.

FIG. 7 is a mesh diagram for the case of analyzing the motor propertiesusing three-dimensional electromagnetic analysis, and the dimensions ofeach portion (circumferential direction average width angle T of theclaw magnetic pole 12, axial direction dimension L1 of the claw magneticpole 12, axial direction dimension L2 of the ring yoke portion 13,circumferential direction dimension H1 in the end extending in the axialdirection 12T of the claw magnetic pole 12, the radial directionthickness H2 in the end extending in the axial direction 12T of the clawmagnetic pole 12, the radial direction dimension F of the permanentmagnetic pole 5, and the circumferential direction space G of the rotor3 and the stator 6) are changed the parameters being studied are shown.

FIG. 8 shows the results of computing the relationship between thenumber of poles M and the output torque (N·m) when the inner diameter D(FIG. 3) of the stator 6 is changed, in the case where the setconditions are such that the radial direction dimension (thickness) F ofthe permanent magnetic pole 5, the removal taper θ of the claw magneticpole 12 is 8 degrees, the radial direction thickness H2 in the endextending in the axial direction 12T of the claw magnetic pole 12 is 2mm, and the ratio of the axial direction dimension (length) L1 of theclaw magnetic pole 12 and the axial direction dimension L2 of the ringyoke portion 13 is a maximum of 5. If the inner diameter D of the stator6 is uniquely set under these limited conditions, it is evident that theoutput torque is the maximum in the specified number of poles M. Thenumber of poles M shifts due to the inner diameter D of the stator 6,and the output torque is maximum when the relationship between the innerdiameter D of the stator 6 and the number of poles M is M=a·D(0.35≦a≦0.5).

Next, a study is carried out of the average angle T in thecircumferential direction of the claw magnetic pole 12 using anexperimental motor with 24 poles and 32 poles as the number of poles Mwhich has the maximum output torque. The computed results of therelationship between the circumferential direction average width angleof the claw magnetic pole 12, T (the circumferential direction averagewidth angle in the axial direction middle of the claw magnetic pole fora ejection taper angle θ of 8 degrees, see FIG. 4) and the output torqueare shown in FIG. 9.

In FIG. 9, when the ratio of the circumferential direction average widthangle of the claw magnetic pole 12, T for the magnetic pitch Pcorresponding to 1 cycle of AC on the horizontal axis is taken and therelationship with the output torque was looked at, it was determinedthat the output torque is maximum at substantially the same angle ratiofor 24 poles and 32 poles. This can determine that in the case where thecircumferential direction average width angle of the claw magnetic pole12 is small, the magnetic flux of the field magnet side cannotsufficiently interlink with the ring coil 10, and conversely, in thecase where it is too large, the leakage of magnetic flux onto theadjacent claw magnetic pole 12 becomes large and the output torque isreduced. In the case where the design of the claw magnetic pole can bedone freely, it is thought that the output torque can be maximized underother conditions, but in the case where the aforementioned limitationsare added to the claw magnetic pole 12, as shown in FIG. 4, the ratio ofthe circumferential direction average width angle of the claw magneticpole 12, T for the magnetic pitch P corresponding to 1 cycle of AC inthe range 0.4-0.45 is the design point that obtains the most stableoutput torque. It is to be noted that the results were the same for thenumber of poles other than 24 poles and 32 poles.

In the above embodiment, a claw pole type motor is described as the clawpole type rotating electric machine, but it is not limited to the clawpole type motor and may also be applied to a generator and the like.

1. A claw pole type rotating electric machine comprising: a ring yokeportion; first and second claw cores which are formed of a plurality ofclaw magnetic poles which are disposed at equal intervals on thecircumference of the inner diameter side of the ring yoke portion andextend in the axial direction; a stator core formed by meshing of theclaw magnetic poles of the first and second claw cores with each other;a stator formed by holding the ring coil on the outer circumference sideof the claw magnetic poles in which the stator cores have been meshed;and a rotor positioned via a space in the circumferential direction atthe inner diameter side of the stator wherein: the first and second clawcores are formed by compacting of magnetic powder; the radial directionthickness of the claw magnetic pole is 2 mm or more; a flat surface isformed perpendicular to the axial direction at the end extending in theaxial direction of the claw magnetic pole; at the claw magnetic pole, aejection taper in the range of 10 degrees or less with respect to theaxial direction is formed as a taper from the base to the end extendingin the axial direction; and the ratio of the axial direction length ofthe claw magnetic pole and the axial direction thickness of the ringyoke portion is no more than 5:1.
 2. The claw pole type rotatingelectric machine described in claim 1, wherein given that therelationship between the absolute value M of the claw magnetic pole andthe inner diameter D of the stator is M=a·D, the coefficient a is set to0.35 or more and 0.5 or less.
 3. The claw pole type rotating electricmachine described in claim 1, wherein the ratio T/P of thecircumferential direction average width angle T of the claw magneticpole and the magnetic pole pitch P which corresponds to 1 cycle of AC isset to 0.4 or more and 0.45 or less.
 4. The claw pole type rotatingelectric machine described in claim 2, wherein the ratio T/P of thecircumferential direction average width angle T of the claw magneticpole and the magnetic pole pitch P which corresponds to 1 cycle of AC isset to 0.4 or more and 0.45 or less.
 5. The claw pole type rotatingelectric machine described in claim 1, wherein the claw core has amagnetic powder density of 7.5 g/cm³ or more.
 6. The claw pole typerotating electric machine described in claim 1, wherein the rotorcomprises a rare earth metal permanent magnet.
 7. The claw pole typerotating electric machine described in claim 1, wherein the rotorcomprises a permanent magnetic pole whose residual magnetic flux densityis 1.2-1.4 tesla.
 8. A claw pole type rotating electric machinecomprising: a ring yoke portion; first and second claw cores which areformed of a plurality of claw magnetic poles which are disposed at equalintervals on the circumference of the inner diameter side of the ringyoke portion and extend in the axial direction; a stator core formed bymeshing of the claw magnetic poles of the first and second claw coreswith each other; a stator formed by holding the ring coil on the outercircumference side of the claw magnetic poles in which the stator coreshave been meshed; and a rotor positioned via a space in thecircumferential direction at the inner diameter side of the statorwherein: the first and second claw cores are formed by compacting ofmagnetic powder; and the magnetic powder density is 7.5 g/cm³ or more.9. The claw pole type rotating electric machine described in claim 8,wherein: the radial direction thickness of the claw magnetic pole is 2mm or more; a flat surface is formed perpendicular to the axialdirection at the end extending in the axial direction of the clawmagnetic pole; at the claw magnetic pole, a ejection taper in the rangeof 10 degrees or less with respect to the axial direction is formed as ataper from the base to the end extending in the axial direction; and theratio of the axial direction length of the claw magnetic pole and theaxial direction thickness of the ring yoke portion is no more than 5:1.10. The claw pole type rotating electric machine described in claim 9,wherein given that the relationship between the absolute value M of theclaw magnetic pole and the inner diameter D of the stator is M=a·D, thecoefficient a is set to 0.35 or more and 0.5 or less.
 11. A claw poletype rotating electric machine comprising: a ring yoke portion; firstand second claw cores which are formed of a plurality of claw magneticpoles which are disposed at equal intervals on the circumference of theinner diameter side of the ring yoke portion and extend in the axialdirection; a stator core formed by meshing of the claw magnetic poles ofthe first and second claw cores with each other; a stator formed byholding the ring coil on the outer circumference side of the clawmagnetic poles in which the stator cores have been meshed; and a rotorpositioned via a space in the circumferential direction at the innerdiameter side of the stator wherein: the first and second claw cores areformed by compacting of magnetic powder; and the ratio T/P of thecircumferential direction average width angle T of the claw magneticpole and the magnetic pole pitch P which corresponds to 1 cycle of AC isset to 0.4 or more and 0.45 or less.